Author

Date of Award

1983

Document Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Abstract

Six serial passages of a cell-adapted strain of EIAV were conducted in Shetland ponies. The 16 recipient ponies became agar-gel immunodiffusion test positive by 25 days after inoculation, and it was observed that the virulence of this cell-adapted strain increased through the successive passages. Clinical signs were closely monitored and recorded, and macroscopic as well as microscopic lesions of EIA were also recorded and evaluated. The effect of EIAV upon blood components was determined after several of the febrile episodes, and the effect of the immunosuppressant dexamethasone on infected ponies were also studied. EIAV was isolated in fetal equine kidney cells cultures from 90% of plasma samples collected during febrile episodes and from 51% of plasmas collected at afebrile periods. The cross serum-neutralization test was carried out for EIAV isolates and sera collected from two experimental ponies. It was found that serum collected shortly after EIAV isolation did not neutralize the virus isolate, but the serum neutralizing activity increased in samples collected thereafter. None of the sera showed neutralizing activity against EIAV isolated after their collection. These results suggest an atigenic change in EIAV occurring in the pony which would allow for the virus persistence in its host. Finally, a study was also carried out to determine whether the mixed culture cytopathogenicity assay, the syncytia infectivity assay, and the reverse plaque assay would be suitable to quantitate EIAV. These assays have been successfully used to titrate several murine leukemia viruses, bovine leukemia virus, and several strains of hog cholera virus respectively. None of these assays, however, was found to be accurate and reliable to titrate EIAV.